Function referring to itself inconsistently question

[Threshold]

I am trying to create a moment and shear force sheet in mathcad but when doing a check I get an error message saying this function refers to itself inconsistantly. Ive attached the sheet, but would like to know how to fix this error as well as clean it up in general.

I should add yes I know the HW question is not complete/finished, as I still have to work it the opposite direction and such. I was just looking for suggestions/help on how to clean it up

Thanks!

[Werner_E]

The error message is misleading.

Your function M2 awaits an unitless argument (otherwise you have a unit mismatch in your subtraction) but you feed it with a range with the unit feet.